Our toilet is simple: We have a 5 gallon bucket. We cut off the top rim of it so it would sit inside ANOTHER 5 gallon bucket. So the top 1/3 or so bucket is affixed to the toilet box cover and the lower one sits below, kept aligned to the upper one by the nesting design of these things. This also keeps the liner in place.
Whenever you use the toilet, you throw in a handful of absorbent material. We've used crushed dry leaves, sawdust (not from treated lumber....it inhibits the decomposition process), pine based cat litter (don't use the clay stuff), and wood stove pellets. As long as you throw in enough to lightly cover what you just...uh...left, there's no odor except one of damp wood. No, really, it doesn't smell. It doesn't. Not at all. My Cat box smells more than the toilet does.
When the lower container is 3/4 full, we pull it out and either put it in the compost bin or throw it in a dumpster (can you do that? What do you think happens to all those disposable diapers?). The last time I tossed it in a dumpster, the bag broke. It looked like a pile of wet oatmeal, no odor but one of decomposing wood, no loose liquids at all.
So then you reline the lower bucket, toss in another 2" of material, and you're ready to continue. With the two of us living on the boat, we dump the thing about every 5 days or so.
As for the biomass, our big accidental find was the hardwood pellets for pellet stoves.
Seriously, folks, this is the absolutely easiest way to deal with your leavings and to meet Coast Guard regs.....
and, really...it doesn't smell.
(check our Morgainne's companion blog to this one, lifeartwater.blogspot.com)